"calculation_range" would be better?

don't use hardcoded values. Keep it in a variable and use that variable it. Will be more flexible and easy for anyone to find modify it he wants.
Also, please add a comment mentioning why items.range / 30 <= 1 is done. Improves readability of the code.

missing spaces between operators and operands.

Put the expressions in parenthesis. Same comment for the ones below.
Improves code readability.

Why not use a nested loop from 0 to 2?

nested loop would be better

The same thing for this formula like I said previously for the one above.

Can you rename these two variables to more understandable names (this one and the one below)?

use .arg() for translation, on some locale, it may not be "3 x" but "3x" or even "x3" or not x at all.
There are also 2 spaces, I think it's 0 in English.

if it's always an int, use int as type. Note that a range is usually two bounds, not a single number, it's more a maxValue here

int?

int?

("%1x").arg(...)
with a comment for translators above please :) (//: comment)

up to

not needed?

is it needed? If no args, it does nothing?

2 spaces after ==